Mutagenesis strategies

(a) F1 screen identifies dominant (b) F3 screen identifies recessive (c) F2 screen identifies recessive mutations. mutations in organisms that mutations in organisms capable cannot self-fertilize. of self-fertilization. i d' +++ d- ' +++ o Mutagenize germ- +++ o Mutagenize +++ o MUtagenlze line progenitors. i sperm cells. Sperm “3”" 9 Allow F1 individuals P9. x a Mate with P 9. x 9 Mfg“? W'th F x to self-fertilize. +++ +++ wild-type +++ +++ W'ld'type 1 +++ +++ Newly lnduced female. female. mutations should F1 i—I—i F1 L—i e isolate F1 be present in both 6 identify progeny and indi- male and female Since each muta- +m+ +++ - gametes. dominant - - — x I Vldually enlzed s rm ls +++ +++ - F . mutations in g - pe mate to W'ld 2 9 Identify reces- - - - unlque, each F1 t e to roduce - F lndIVlduals. ~ - - - Y9 P Slve 1 lhleldual cames . . - - ' separate F2 mutatlons in F dlstlnct Induced families . d' 'd | 2 Dominant mutations mutations. I m M ua 5' segregate 'n a 1:1 ratlo. +m+ 9 interbreed F2 Homozygous mutants may not segregate I:2 x “+++ individuals to 3:1 in F2 generation if F1 individuals are produce F3 mosaics with some wild-type cells and l—I—l progeny. some heterozygous mutant cells, as is the 6 Identify case when plant seeds are the starting F3 recessive material for mutagenesis. mutations in F3 individuals. Only some matings are between two heterozygous F2 individuals. In F3 crosses where both parents are heterozygous, a 3:1 ratio of wild-type to mutants is observed. If either F2 is wild-type, no recessive phenotype will be seen.